Like Emmerman, other professional riders all seem to have their own strategies for coping with the sensation. Jens Voigt, often seen on the front of the peloton with the face of a man whose toenails are being plucked out with hot pliers, relies on a Teutonic mantra: “Shut up, legs!” Lewis feels his greatest enemy isn’t the pain in his legs, but his brain and its expectations. “If you get to the limit where you thought you would give up, your body shuts down,” he says. “You’ve already convinced yourself, that’s it.”

In retrospect, that’s what happened to me when I took San Millán’s test. I figured I had to make it to about 3.5 watts per kilogram to avoid undue ridicule from the readers of BICYCLING—almost as if giving myself permission to quit there.

Lewis’s approach to managing his suffering is to imagine folding it up then sticking it into one of the pockets on the back of his jersey. “If you keep going,”he says, “it can be almost not a big deal to go through it. Then keep going up the next switchback, then worry about the next kilometer. The pain kind of subsides after a certain point.”

Other riders devise more elaborate scenarios. At the Tour of California one year, I rode in a team car behind Garmin rider Dave Zabriskie during the Solvang time trial. Zabriskie is one of the best time-trialists precisely because he has an inhuman ability to force himself to suffer. But his coaches said not one word to him throughout the 30-minute effort; there was no yelling, no “Venga! Venga!” Just radio silence.

Once in a hot race when I was going as hard as I possibly could, I looked down at my heart monitor and saw a blinking, and terrifying, 212. My solution was to stop wearing the monitor in races.

“Dave doesn’t want any information,” explained Allen Lim, who was then Garmin’s team physiologist. Zabriskie’s suffering all takes place internally, measured to his own feedback, ­although he’s not exactly alone in there. “When he’s in a time trial,” Lim said, “he thinks of himself as a superhero.”

The common factor in all the approaches is focus: If you’re asking grand existential questions, you’re in trouble, which might be why poets don’t make good bike racers, and vice versa.

But there are also rare times when suffering—sorry, “physical discomfort”—just seems to vanish entirely: when you’re perfectly trained, and you’re on top of the gear and far from thoughts of surrender and defeat. Emmerman says her patients describe it as a zone of total detachment, where the body’s feelings of pain barely even register in the consciousness. “That’s the zone you want to be in,” says Zabriskie’s teammate Christian Vande Velde. “You drain out all the fans, everything, even the director; and it’s everything that you’ve trained yourself to do for the last 20 years of your life, and you’re just pretty much on autopilot.”

Vande Velde is legendary for mediocre performances in fitness tests—and killing it in races. “The physiologists would look at his numbers and say, ‘I don’t know how this guy finishes top 20 in the Tour,’” says Jonathan Vaughters, his team director. Yet there he was in the 2008 Tour de France, in third place after two weeks, right behind Cadel Evans and ahead of both Schleck brothers. Then came the crucial first day in the Alps, which finished on a sharp climb. When the pack hit the base of the climb, 100 guys suddenly became 12, then eight. Vande Velde was right there. He followed the wheels, swinging across the road to cover ­everything. “You had to follow the attacks all the way, pushing yourself so far,” he says. “When somebody attacks, you just jump.”

When he got to the top, the finish, he sat there for 15 minutes, straddling his bike and digesting what had happened. It took a while before he felt ready to ride back down to the base, where the team buses waited. He’d slipped a spot in the overall standings, to fourth, but he had dropped Evans and he knew now that he could hold his position all the way to Paris. It was the best racing day of his life, and he barely felt—or saw—a thing.

“Coming down the hill,” he remembers, “I’m like, holy crap, where did all these people come from? There were half a million people on the hill that day, and I hadn’t seen a single one of them.”

BUT IF SUFFERING can simply disappear like that, like it did for Christian Vande Velde, then what is it, really? An experience like that seems to imply that suffering is more complex than either physical limits or a central governor.

Among scientists, the debate between proponents of “central” and “peripheral” fatigue is as nasty as it is unresolved. An editorial in the journal Sportscience sneered at “The Improbable ­Governor,” while in a 2009 issue of Sports Medicine, Noakes’s most ­vocal opponent, Roy Shephard, MD, PhD, published an article wondering, “Is It Time to Retire the ‘Central Governor’?”